SCHOTT solutions no. 2/2009 > Astronomy

Professor Hideyo Kunieda und Studenten der Nagoya University zeigen eines der Duran® Spezialglasrohre von SCHOTT, die zum Bau des zentralen Teils des Röntgenteleskops von Astro-H benötigt werden. Photo: H. Kunieda

An X-ray View of the Universe

Duran® glass tubes ensure super-smooth surfaces for building conical mirrors.

Gerhard Samulat

Current plans call for the Japanese carrier rocket H-IIA to blast off from Tanegashima Space Center with the Astro-H satellite on board in the winter of 2014. Its sensitive x-ray sensors will then be gazing into the depths of the universe at an altitude of about 550 kilometers above Earth. They will be on the lookout for distant galactic phenomenon, like black holes, but also gigantic plasma clouds that could one day give birth to stars or even entire planets. Duran® borosilicate glass tubes from SCHOTT ensure that the sky scout will be able to see everything clearly.

“Astro-H will be examining celestial objects, such as massive black holes hidden behind thick dust and gas walls, just like an x-ray machine,” explains Hideyo Kunieda. He is a professor at Nagoya University, an institution that has already produced two Nobel Prize winners in physics. Kunieda is the person responsible for developing this artificial satellite. This is why he visited SCHOTT-Rohrglas in Mitterteich, Bavaria, in the summer of 2009. His researchers have ordered more than 100 Duran® glass tubes of between 120 and 415 millimeters in diameter and one and a half meters in length. “We need these special glass tubes to be able to build the main part of our x-ray telescope,” Kunieda explains.
Graphic look into the future: As of the end of 2014, the Astro-H 550 satellite is expected to begin gazing into the universe 550 kilometers above the Earth. Duran® borosilicate glass from SCHOTT allows its x-ray eyes to see sharply. Photo: JAXA
X-ray light cannot be focused to form a sharp image using normal lenses. The refractive index of this part of the electromagnetic spectrum is nearly the same for the vacuum. X-rays can be bundled using conically tapered cylinder mirrors with a high density metal coating on a super-smooth substrate. This is why the Japanese astronomers are using the Duran® glass that Otto Schott invented at the end of the 19th century as their model. With roughness of only a few atomic diameters in height, the surface of this glass is almost perfectly smooth. Japanese technicians vapor deposit various metal coatings onto it, bond them together and remove them from the glass once again to obtain their glossy mirrors. “We tested glass tubes from several manufacturers, but the best ones came from SCHOTT!” Kunieda says. And he certainly knows what he is talking about: the Japanese space agency already used special glasses from SCHOTT for the space telescope Suzaku, the predecessor to Astro-H.

If it would be possible for us humans to see x-rays, we would be looking into the evening sky with completely different eyes. We could see through galactic fog or clouds of dust just as doctors are able to view our bones through tissue made of flesh and skin. And like doctors, astronomers are using x-ray satellites to expand their view from the surface to the depths. Nevertheless, they are not interested in learning more about how healthy the universe is – at least there are no signs of any real deficiencies. More importantly, these sky scouts are hoping to learn more about exotic objects like black holes, galactic particle accelerators and the dynamics of hot plasma from which the planets or stars perhaps originate. “We thus learn more about the history of our origins and probably even our fate,” Kunieda explains.

These types of observations cannot be made from here on Earth. Our atmosphere does not allow this part of the electromagnetic spectrum to pass through. And luckily so! After all, life never would have been able to develop while our planet was being bombarded with hard x-rays that also lash down on us from the sun. With a weight of 2.4 tons and a length of 14 meters, Astro-H (here the “H” indicates that it is the eighth astronomy satellite) ranks as the largest and heaviest satellite that the cosmologists from the “Land of the Rising Sun” have ever sent into space. Astro-H, which its creators also affectionately call NeXT (for New X-ray Telescope), is a co-production of the American space agency NASA and Europe’s ESA under the leadership of the Japanese space agency JAXA. <|